This invention relates to a medical appliance for the treatment of a portion of body vessel by ionizing radiation, comprising a catheter, an inflatable elongated balloon distally surrounding the catheter, and lumen means longitudinally extending through the catheter for positioning a radioactive radiation emitter within the balloon.
U.S. Pat. No. 5,213,561 describes a device for preventing restenosis after angioplasty comprising, among various embodiments, a catheter having a balloon at its distal end and a center core or tube in which a conventional guidewire is receivable. Particles or crystals of radioactive material are embedded in or mounted on the tube inside the balloon and a retractable shielding sleeve is slidable along the tube to cover the radioactive source, blocking exposure to radiation until it is shifted away. Such a structure is said to allow radiation of a vascular structure immediately following completion of angioplasty, without separately inserting a radiation source.
Standard dilatation balloons are not well suited to transport and to take up radioactive radiating sources because the center core or guidewire lumen tends to warp on the stretch inside the balloon, thereby forming an undulated line. The radioactive radiation source, however, has to be centered as exactly as possible inside the vessel in order to avoid the vessel wall being burned.
The document DE-9102312.2 describes balloon catheters for performing angioplasty procedures followed by radioactive irradiation to prevent restenosis. In a first embodiment, there is provided a catheter closed at its distal end and bearing a dilatation balloon which can be inflated by a fluid medium supplied via a lumen extending longitudinally of the catheter; a radioactive seed affixed to the end of a guidewire may be inserted into the catheter lumen to be brought into the site of angioplasty while the balloon is inflated; according to a variant, the lumen of the catheter may be separated in two parallel channels by a longitudinally extending intermediate wall, one of the channels being for insertion of the fluid for inflating the balloon and the other for insertion of a guidewire having the radioactive seed affixed at its end. In a second embodiment, the catheter comprises an additional channel centered in the catheter lumen by means of two longitudinally extending intermediate walls; the catheter lumen is thus divided into three channels, of which the central channel is for insertion of a radioactive pin affixed at the end of a guidewire and the lateral channels for balloon inflation and for supplying drugs into the blood vessel, respectively. In a third embodiment, the catheter bears two balloons at a distance from one another and which can be inflated separately; the catheter also comprises a central channel centered in the catheter lumen by means of four longitudinally extending walls defining four channels surrounding the central channel; two of the surrounding channels are respectively opening into the balloons for inflation thereof, and the two other surrounding channels are respectively opening between the two balloons to allow injection of drugs in the vessel area comprised between the two balloons; the document indicates that a radioactive seed affixed to the distal end of a guidewire may be placed in the lowest of the surrounding channels; the document also indicates that the radioactive source may be placed in the central channel, further outlining that, as with the second embodiment, the radioactive source may even be driven out of the catheter to directly irradiate the vessel. Apart from the fact that this document does not consider any particular centering of the radioactive source in the body vessel, its various configurations do not allow such a centering.
In the first embodiment of this document DE-9102312.2 no measures are described which would ensure circumferentially uniform radiation impact on the vessel wall and the radial position of the irradiation source is merely determined by gravity, whereby warping of the catheter lumen upon inflation of the balloon will add to the unevenness of radiation distribution in the vessel. In the second embodiment, any warping upon inflation of the balloon will be fully uncontrollable because of the different reactions of the main channel, additional channel and longitudinal walls of the catheter to the stresses resulting from the stretch inside the balloon; this of course makes it impossible to know where and how the radioactive radiation will be distributed in the vessel. In the third embodiment, the situation shows the same drawbacks as for the second embodiment, with some more uncertainty resulting from the additional channels.
The document DE-3620123-A1 discloses an apparatus for measuring and irradiating body cavities which permits the placing and positioning of a light conductor at the center of a cavity in order to achieve homogeneous lighting thereof via a dispersing agent.
To this effect, a light conductor is located in a tubular catheter surrounded by two optically transparent centering flexible balloons at a distance from each other and which are inflated by a dispersing agent in order to have them rest against the wall of the body cavity. The portion of the catheter which is located between the balloons is stiffer than the rest of the catheter to avoid modification of the distance between the two balloons, for instance due to curving of the catheter. The system is said to be usable for a blood vessel, and the two balloons are occlusion balloons. Occlusion balloons have to be resilient to safely fulfill their task in a vessel of unknown exact shape and size. Because of this resiliency, occlusion balloons can not be used simultaneously as dilatation balloons. Resilient balloons would overstretch the vessel wall when used with the higher pressures that are required for a successful angioplasty. Of course the doctor has control over the inflation pressure with resilient balloons same as with dilatation balloons, but this is not sufficient for safe angioplasty. With a resilient balloon the doctor has no control over the inflated diameter or over the shape to which the balloon is inflated. Of course, with this apparatus the source could be centered if the balloons are close together, but the additional weldings of two balloons close together make the catheter more complicated and expensive. Furthermore, the added weldings reduce the flexibility of the catheter which is necessary to maneuver it through tortuous vessels and to use it in tortuous vessels.
The purpose of this invention is to improve the conditions of radioactive radiation treatment of body vessels by proposing a medical appliance with inflatable balloon for a vessel wall radiation which is uniform around the vessel, an appliance that is highly versatile, simple to manufacture and easy to use.
In the present invention, a waist centers the lumen containing the radioactive radiation emitter inside the body vessel at least at the location thereof and substantially eliminates any undulated shape which may be taken by the catheter or lumen containing the radioactive radiation emitter. The stretch occurring upon inflation of the balloon therefore does not affect the positioning of the radioactive radiation emitter within the body vessel. And the appliance may retain a good flexibility allowing its maneuver and use in tortuous and/or narrow vessels.
Specifically, it becomes possible to improve dosage control of the radioactive radiation with regard to the distance between radioactive source and vessel wall, whereby overdosage because of too narrow distance and underdosage because of too wide distance to the vessel wall is avoided, and the impact of radiation on the vessel wall is essentially uniform.
The waist may be created by belt means which may be regularly or irregularly spaced from one another over the length of the balloon in order to match any structural configuration and warping tendency of the catheter and balloon assembly.
For inexpensive fitting of existing balloon catheters, the belt means may be made of surgical thread, possibly surgical thread tied with a knot.
To modulate the centering of the catheter within the balloon, the belt means may be made of molded rings, the length and thickness of which will be chosen as a function of the strength needed to counteract the warping tendency of the catheter.
For safety purposes, the lumen means may have a narrowed distal end whereby the catheter may be normally guided along a guidewire while the radioactive radiation means may be sufficiently thick for not passing through the narrowed distal end. Similarly the lumen means may be closed distally.
The waist or belted balloon catheter may be adapted to several practical configurations, for example to allow use of the technology known under the trade mark MONORAIL. In this case, the lumen means may be closed distally, and the catheter may further comprise a guidewire lumen with an entry and an exit distal of the balloon, which advantageously results in a two lumen catheter construction which will be easily centered within the balloon by the belt means. The catheter may also comprise a guidewire lumen with an entry distal of the balloon and an exit proximal of the balloon, the three lumen catheter so achieved being also correctly centered within the balloon by the belt means.
In sum, the present invention relates to a medical appliance for the treatment of a portion of body vessel by ionizing radiation with a catheter, an inflatable elongate balloon distally surrounding the catheter, and lumen means longitudinally extending through the catheter for positioning a radioactive radiation emitter within the balloon. A waist on said balloon essentially centers the catheter within the balloon. The belt means may create the waist, and may be regularly spaced from one another over the length of the balloon or irregularly spaced from one another over the length of the balloon. The belt means may be made of surgical thread, which may be tied with a knot. The belt means may be made of molded rings. The belt means may be affixed to the balloon, such as by adhesion. The lumen means may have a narrowed distal end, and may be closed distally. The catheter may further have a guidewire lumen with an entry and an exit distal of the balloon, or a guidewire lumen with an entry distal of the balloon and an exit proximal of the balloon.
In an alternative embodiment, the present invention relates to a catheter that may have an elongate tubular member having a distal portion with an outside diameter; an at least partially expandable balloon configured on the distal portion of the tubular member, the balloon having a distal end, a proximal end, and at least one intermediate segment therebetween; and balloon expansion restriction means for limiting the expansion of at least one intermediate segment so that the segment does not substantially expand. The catheter may also have an elongate tubular member; and a balloon configured on the tubular member, the balloon having a proximal segment, a distal segment and at least one intermediate segment wherein the proximal and distal segments are inflatable to diameters which are greater than the inflatable diameters of the at least one intermediate segment. In another embodiment, the catheter may have an elongate tubular member having an outside diameter; an at least partially expandable balloon configured on the tubular member; a first zone on the balloon, inflatable to a first inflated diameter; and a second zone on the balloon, inflatable to a second diameter; wherein the second diameter is essentially the same diameter as the outer diameter of the tubular member.